1. Field of the Invention
My invention relates to transmissions or drives for the transfer of power from one shaft to another, and in particular to a variable speed transmission permitting the speed ratio of the shafts to be varied infinitely or continuously. The variable speed transmission according to my invention is adaptable for use with machine tools, motor vehicles, and a variety of other pieces of machinery.
2. Description of the Prior Art
There have been suggested and used many and varied methods of providing a variable speed output for driving a desired piece of machinery. Basically, such methods are either (1) mechanical, (2) hydraulic, or (3) electrical. Numerous forms of these basic methods exist, however, resulting in considerable difficulty in choosing a particular drive or transmission assembly for any intended application.
While each variable speed drive of prior art design may be admirably suitable for certain specific applications, it also has one or more of such drawbacks as poor efficiency, low output torque, narrow speed range, noncontinuous or stepwise speed change, and necessity for stopping the machine in order to change speed.
More recent developments in electronics have widened the choice still further by employing the thyristor, or silicon controlled rectifier, in association with a direct current motor to provide an infinitely variable drive system. This advanced system is also not free from certain disadvantages, however, such as high capital cost and comparatively low output torque at low speed. Its use in applications demanding a wide speed range is also subject to a question.